US drug maker Merck announced on Friday, 1 October that an experimental pill it developed to treat COVID-19 reduced the risk of hospitalisation and death by nearly half in a clinical trial.
With COVID-19 vaccines being administered all over the world, scientists are working on a pill that can fight the virus early after diagnosis, prevent symptoms from developing post exposure.
While vaccines aim to prevent infection and the most effective way to reduce chances of adverse symptoms, oral pills can speed up recovery and stop the virus shortly after exposure. It could also be taken at home, reducing the burden on hospitals.
"Oral antivirals have the potential to not only curtail the duration of one's covid-19 syndrome, but also have the potential to limit transmission to people in your household if you are sick," Timothy Sheahan, a virologist at the University of North Carolina-Chapel Hill who has helped pioneer these therapies, was quoted as saying by CNN.
How do these antiviral medications work?
Oral antivirals are already in use for other viral infections like hepatitis C and HIV. A popular antiviral is Tamiflu which can shorten the duration of influenza and reduce the risk of hospitalisation.
Basically, they hinder the virus's ability to replicate in human cells, CNN reported.
Which are the antiviral drugs in the race?
At least three promising antivirals for COVID-19 under clinical trials and the results are expected in the coming months, Dieffenbach, director of the Division of AIDS at the National Institute of Allergy and Infectious Diseases, who is overseeing antiviral development, was quoted as saying by CNN.
Merck & Co. and Ridgeback Biotherapeutics - molnupiravir
Pfizer's PF-07321332
Roche and Atea Pharmaceuticals' AT-527
How does Merck's molnupiravir work?
In the case of molnupiravir, the enzyme that copies the viral genetic material is forced to make so many mistakes that the virus can't reproduce. This reduces viral load and cuts down the infection time and serious illness, CNN reported.
Molnupiravir is taken within five days of onset of COVID-19 symptoms, twice a day for five days, according to Financial Times.
Merck and partner Ridgeback Biotherapeutics said they plan to seek US emergency use authorisation for the pill as soon as possible and to make regulatory applications worldwide.
How does Pfizer's antiviral drug work?
US pharma group Pfizer is studying two antivirals – a tablet that a tablet that can be taken at home and an intravenous infusion for patients suffering from more serious disease, according to Financial Times.
The medicines work by blocking the enzyme that the the virus needs in order to replicate in the body.
The drug, which would could be a game changer if proven effective, may be available in the markets by the end of this year.
What about Roche and Atea Pharmaceuticals' AT-527?
Roche and partner Atea Pharmaceuticals in June said early data from a trial of their experimental oral antiviral AT-527 showed that it lowered viral load in hospitalised patients.
AT-527 is an oral direct-acting antiviral agent developed from Atea’s nucleotide prodrug platform. The antiviral drug blocks viral RNA polymerase, which is needed for viral replication.
Atea officials said they expect results from phase 2 and phase 3 trials later this year.
Is any antiviral drug used to treat Covid currently?
So far, only one antiviral drug, remdesivir, has been approved to treat COVID-19. However, it is not used orally but given intravenously to patients ill enough to be hospitalised, and is not intended for early, widespread use.
(With inputs from CNN & Financial Times.)
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